Yams are an important food crop in many countries. The most common crop in Africa is celebrated at the Yam Festival where yams are offered to gods and ancestors before being distributed to the villagers. In the United States, yams are associated with Thanksgiving and Christmas. Although many people think that sweet potatoes are the same as yams, they are an entirely different vegetable and not related botanically.
Yams were the most common staple fed to African slaves. Yams were carried in slave ships from Africa to North America for consumption during the long passage to the New World. Over time, yams were integrated into western culture as a staple cuisine. The slave merchant, John Barbot, claimed that for every 500 slaves, more than 100,000 yams must be carried. An accounting of the slave ship "Othello" in the 1700s listed hundreds of baskets of yams taken on board as provisions, along with lesser quantities of other foods.
Protein in Yam
Normally vegetable protein such as that found in yams is poor quality when compared to protein in meat. However, what makes yams unique is a major tuber storage protein called dioscorin, which has antioxidant properties and immunomodulatory activity, according to a 2009 study by the School of Pharmacy, Taipei Medical University, Taiwan.
Benefits of Dioscorin
Not only do yams provide a good source of potassium, but also the storage protein, dioscorin, which may benefit individuals with hypertension. Dioscorin may inhibit an angiotensin-converting enzyme that increases kidney blood flow and lowers blood pressure, according to Gomestic website. According to a report published in “Journal of Agricultural and Food Chemistry,” findings of a study suggested that eating or consuming yams in supplements is a health benefit resulting from dioscorin’s role as an antioxidant in the tubers.
The Chuin type yam is a protein-rich starch staple diet in Peru as a result of the bean, not the root of the plant. This yam has an extremely high production of seeds containing concentrations of rotenone, mildly toxic when eaten raw. But when made into flour, the rotenone is removed from the seeds, which provide a strong protein source as well as seed oil, according to the American Society of Agronomy. Studies have identified yam types with high storage root production, high protein and high starch contents -- containing three to five times more protein than potatoes or other yams. In addition, the storage roots can be processed into granular flour. Ongoing research at the International Potato Center continues to determine potential for providing high quality food production needed in Africa.
Throughout history, the wild yam has been used as a traditional herbal medicine. Wild yam is claimed to be a natural alternative to estrogen therapy to relieve menopausal symptoms. The root and the bulb of the wild yam are used to prepare an extract of dioscorin for helping to treat diverticulosis, diseases of the gallbladder, rheumatoid arthritis and fatigue. The Natural Medicines Comprehensive Database says more evidence is needed to rate wild yam for effectiveness, according to Medline Plus.
- PubMed.gov: Effects of Oral Administration of Yam Tuber Storage Protein, Dioscorin, to BALB/c Mice for 21-Days on Immune Responses; Liu YW et al.; 2009
- Goestic: Do You Know the Difference Between a Sweet Potato and a Yam?
- “Journal of Agricultural and Food Chemistry:”Antioxidant Activities of Dioscorin, the Storage Protein of Yam (Dioscorea batatas Decne) Tuber; Wen-Chi Hou et al.; 2001
- EurekaAlert: Yam Bean a Nearly Forgotten Crop
- Medline Plus: Wild Yam